Conservation Research Laboratory: General Conservation Projects

Nicolas Ramos-Lara

Time Period: August 2004 – May 2008

Location: Sierra de San Pedro Mártir, Baja California, Mexico

Major Questions: 1. What is the current situation of the arboreal squirrels of Mexico (review chapter)
2. Do Mearns’s squirrels have specific habitat requirements for nesting?
3. Do home-range dynamics and habitat use of Mearns’s squirrels differ from other congeners?
4. Do life-history and behavioral tactics of Mearns’s squirrels differ from other congeners?

Major Findings: 1. In Mexico, there are 14 recognized species of arboreal squirrels of which four are endemic, with the states of Chiapas and San Luis Potosi possessing the greatest diversity.
2. Presently, all species are listed under some category of risk by IUCN, seven by Mexico’s SEMARNAT, and only one by CITES.
3. Our literature survey yielded 37 publications revealing that a dearth of scientific information still exists on the arboreal squirrels of Mexico.
4. States with a greater diversity of arboreal squirrels also have higher annual wood productions, which may pose a serious threat to their persistence.
5. Mearns’s squirrels rely primarily on tree cavities for nests, with nest tree species, nest tree condition, nest tree size (DBH), canopy cover, and occurrence of white firs (Abies concolor) as important characteristics of the habitat for nesting.
6. Without larderhoards (middens), home-range dynamics of Mearns’s squirrels are similar to nonterritorial squirrels of the genus Sciurus, suggesting that middens played an important role in the evolution of territoriality in Tamiasciurus.
7. Using satellite imagery, I found that remote areas in the Sierra de San Pedro Mártir appear to have suitable habitat for the species.
8. Survival of adult Mearns’s squirrels was influenced by sex and body mass.
9. Mearns’s squirrels are heavier and apparently also larger than other congeners, possibly in part as an adaptation to feed on large pine cones (Pinus).
10. Interyear variation in weather and food supply strongly influenced fitness-related traits and behavior of Mearns’s squirrels.